Pressure observer



March 2s, 1944. M, F, REYNST TAL 2,345,071

PRESSURE OBSERVER Filed Feb. 26. l1941 Patented Mar. 28, 1944 PRESSUREOBSEBVEB Maximilien Felix lteynst, lierre Binia, Willem Hendrik Stigter,and Cornelis Dorman, Eindhoven, Netherlands; vested in the AllenProperty Custodian Application February 26, 1941, ASerial No. 380,745 VIn the Netherlands January 13, 1940 Claims.

For pressure measurements use is often made of a diaphragm which isexposed to the pressure to be measured and which constitutes one of theelectrodes of a condenser in which the distance between the twoelectrodes consequently varies with the pressure to be measured. l

Usually this condenser is screwed, either directly or set in a holder,Into a hole in the wall of the vessel in which the pressure variationsmust be watched such as, f or example, the cylinder portion of aninternal combustion engine.

Of Acourse it is desirable that the capacity of the condenser be actedupon solely by the` pressure to be measured and, for instance,'not alsoby temperature variations nor by strains set up in the material upontightening screws. v

The present invention provides a constructie by which these conditionsare satisfied.

According to the invention the diaphragm cony stitutes the bottom pf acylindrical tube which is freely suspended in a. bore of the holder andwhich makes a tight ilt with this holder at the top.

The bore of the holder may be closed by a perforated bottom.

Further particulars of the invention may appear from the following, inwhich one form of construction of a pressure observer according to theinvention is described by reference to the accompanying drawing.

A steel holder I has a polygonal, for instance a hexagonal top portion,whereas its bottom portion is furnished with 4an external screw threadby means of which the holder can be screwed into a wall, for instance acylinder wall. The holder has an internal cylindrical bore which at thetop Is wider than at the bottom. The upper 4wide part is internallyprovided with a screw thread, in which is screwed a hollow steelcylinder 2 whose bottom portion 4 is so much narrower as to spacedly fitin the lower base of the holder i, forming between these members a thinannular cylindrical cavity. A shoulder of the cylinder 2 rests on acopper ring 3 together with which it forms a gas-tight closure. At thebottom the cylinder 2 is closed by a diaphragm 5 made from thin specialsteel' and secured by welding. The flat part of this diaphragm coactswith a metal plate l closely `arranged above the diaphragm forms acondenser whose capacity depends on the prevailing deection of thediaphragm. The plate i is secured to the bottom of a thickened part 1 ofa metal shaft 8 on which is slipped a small cylinder Il ofceramicmaterial which by means of a collar 8 and a s'et screw is keptpressed against the thickened part 1. The cylinder III fits in the boreof cylinder 4v and is pressed at the bottom against a re-- entrant edgeof this cylinder by means of a thrust piece II and a ring I2 screwedinto the cylinder 2.

For reasons stated hereinafter the bore in the holder I does not extendto the bottom, but there is left a wall I3 having a thickness of severalmllimetres in which are provided a number of perforations I4. Obviouslythe distance between thel parts 5 and 6 is entirely independent of theforce with which the holder is screwed into the wall of the cylinder,but also of the force with which ythe cylinder 2 is fastened andtightened in the holder. 'A suitable choice of the material of parts 4,5, 6 and I results in that'the air-gap between 5 and 6 does not changeon the occurrence of temperature variations.

When the pressure`observer is ,used on the cylinder portion of aninternal combustion engine 'in which, of course, high temperatures occurprovision must be made for suiilcient cooling of the diaphragm and/orfor adequate protection thereof against the hot gases. Cooling lcan bepromoted by coating the parts 4 and 5 with a layer or foil of a metal ofhigh thermal conductivity such-as copper or silver. vProtection of thediaphragm from the hot gases is primarily aorded by the perforated wallI3 and in addition, if required, by inserting one or more mica` platesbetween the said wall and the diaphragm 5. We wish it to -be understoodthat we do not desire to be limited to the exact details or constructionand design shown and described as various modiilcations oi the inventionwithin the scope of the appended claims may occur to a person skilled inthe art.

What we claim is:

1. A device for measuring variations in pres- A sure of a fluid within acontainer, comprising a housing provided with a bore exposed to thefluid, means vcomprising a portion of said housing to secure the same tothe container, and a pressureactuated mechanism comprising a casingpositioned within and spaced from the surface oi said bore adjacent tosaid securing means-and a pressure-actuated diaphragm member closing oneend of said casing and ladapted to be acted upon by the fluid, saidcasing being secured to said housing at a portion remote from saiddiaphragm and outside the vicinity of said securing -means to therebypreclude distortion oi said diaphragm by stresses applied to thesecuring means of the housing and of the casing.

2. A device for measuring variations in pressure of a iuid within acontainer, comprising a metal housing provided with a central boreexposed to the fluid, means comprising a threaded end portion of saidhousing-to secure the same to the container, and a pressure-actuatedmechanism comprising a tubular metal casing positioned within said boxeand spaced from the surface thereof at a portion adjacent to saidthreaded portion, a pressure-actuated diaphragm-shaped electrode closingone end of the casing and having an outer surface adapted to be actedupon by the iiuid, and a counter electrode positioned within said casingadjacent to the inner surface of said diaphragm-electrode, said casingbeing secured to said housing at a portion remote from said diaphragmand outside the vicinity of said threaded portion to thereby precludedistortion of said diaphragm by stresses applied to the said threadedportion and to the securing means of said casing.

3. A device for measuring variations in pressure oi' a fluid within acontainer, comprising a housing provided with a bore having one endthereof exposed to the fluid, a perforated wall portion covering thesaid end of the bore, means comprising a portion of said housing tosecure the same to the container, and a pressure-actuated mechanismcomprising a casing positioned within and spaced from the surface ofsaid bore at a portion adjacent the securing means of the housing andl apressure-actuated diaphragm member closing one end of the casingpositioned adjacent to and spaced from said perforated wall portion,said casing being' secured to said housing at a portion remote from saiddiaphragm and outside the vicinity of said securing means to therebypreclude distortion of said diaphragm by stresses applied to thesecuring means of the housing and of the casing.

4. A device for measuring variations in pressure of a fluid within acontainer, comprising a housing provided with a bore having one endthereof exposed to the mud. a perforated wall portion covering the saidend of the bore, means comprising a portion of said housing to securethe same to the container, and a pressure-actuated mechanism comprisinga casing positioned within and spaced from the surface of said bore at aportion adjacent to the securing means of the housing, apressure-actuated diaphragm member closing one end of said casingpositioned adjacent to and spaced from said perforated wall portion, anda layer of a material of high thermal conductivity forming a coating onthe surface of said electrode, said casing being secured to said housingat a portion remote from said diaphragm and outside the vicinity of saidsecuring means to thereby preclude distortion of said diaphragm bystresses applied to the securing means of the housing and of the casing.

5. A device for measuring variations in pressure of a fluid within acontainer, comprising a housing provided with a bore having one endthereof exposed to the fluid, a perforated wail portion covering thesaid end of the bore, means comprising a portion of said housing tosecure the same to the container, a pressure-actuated mechanismcomprising a casing positioned within and spaced from the surface ofsaid bore at a portion adjacent to the securing means of the housing anda pressure-actuated diaphragm member closing one end of the casingpositioned adjacent to and spaced from said perforated wall portion, anda heat-resistant baille member interposed between said diaphragm memberand the perforated wall, said casing being secured to said housing at aportion remote from said diaphragm member and outside the vicinity ofsaid securing means, to thereby preclude distortion of said diaphragm bystresses applied to the securing means of the housing and of the casing.

FELIX REYNST. HEERE RINIA.

WILLEM HENDRIK SI'IGTER. CORNELIS DORSMAN.

